It is well-known that transformer cores consist of laminations placed one on top of the other, divided up into layers which are suitably staggered so that the lines of the joints never fall on the same plane. This invention refers in particular to an automatic assembling machine capable of setting up transformer cores of the type with three columns, that is to say with a left column 1 on one side, a right column 2 on the other side, a central column 3, a lower yoke 4 and an upper yoke 5 (see FIG. 1).
Naturally definitions "right", "central", "left", "upper" and "lower" are used only for the purpose of simplifying the following description.
FIG. 1 illustrates schematically a plan of this type of transformer core.
In setting up the core of a transformer, the upper yoke is fitted in a subsequent stage, and therefore the automatic assembly system according to this invention refers only to the assembly of the laminations forming the three columns and of the lower yoke.
As shown in FIG. 2, each element of the core, whether yoke or column, is made up of several steps (11 in the figure), always an uneven number, numbered here for reference purposes from G1 to G11, in such a way that the transverse section of each element of the core may be inscribed approximately within a circumference.
Obviously the central step G6 is thicker, while the remaining steps are arranged symmetrically on each side of this central step.
Each step is made up of several layers of identical laminations, the number of which is generally comprised between 2 and 4.
The succession of the various layers forming the core can be arranged in two different ways, known as "simple superimposition" and "complex superimposition".
FIG. 3 shows the simple superimposition pattern: the continuous lines indicate the positions of the identical and superimposed laminations of the i-th layer; the dotted lines indicate the positions of the identical and superimposed laminations of the (i-1)-th and (i+1)-th layers.
In this configuration the laminations of each successive layer occupy alternately one or the other of the two positions shown.
FIG. 4 illustrates the complex superimposition pattern: the continuous lines on the ends of the columns and of the lower yoke, and in the central area of the lower yoke indicate the positions of the laminations of the central layer; the dotted lines, on the otherhand, indicate the positions of the layers overlying and underlying said central layer, the ends of which are cut asymmetrically, staggered between pre-established minimum and maximum values.
The laminations in the side columns and in the bottom yoke for each single step are all identical to one another but, layer by layer, they are assembled staggered in a longitudinal direction.
The laminations of one and the same step of the central column are identical, but they are assembled in the opposite position, with the layers arranged symmetrically in relation to the central layer.
The laminations forming the core are made from grain-oriented silicon steel sheeting of a suitable thickness, usually between 0.2 and 0.4 mm.
The laminations are obtained from these sheets by blanking, after which they are packed on metal platforms in reverse order as compared to the sequence in which they will have to be piled for forming the various elements of the core (see FIGS. 5 to 7). From the platforms 7, 8 and 9, the laminations are taken to a suitable supporting frame 10, which has uprights 11, 12 and 13 and cross-members 14 and 15 reproducing the shape of the transformer core.
Indeed, the laminations of columns 1, 2 and 3 have to be transferred onto the uprights 11, 12 and 13, while the laminations of the yokes 4 and 5 have to be transferred onto the cross-members 14 and 15.
The supporting frame 10 must be suitably shaped and sufficiently strong to allow the operations to which the transformer core must be subjected after correct piling of the laminations.